Device for reducing the entry of fluid into a tunnel

ABSTRACT

The device for controlling the flow of fluid passing in front of an orifice or cavity produced in the hull of a vessel has at least one deflector ( 5 ) rigidly fixed to the wall of the vessel upstream of the orifice or cavity. This deflector has a planar inner face directed towards the hull of the vessel and a curved outer face which is highly convex upstream and tapered downstream.

The present invention relates to a device greatly reducing, or evenavoiding, the entry of a fluid, generally a liquid, into a tunnel. Inparticular, the invention relates to a device enabling—during the normalforwards movement of a vessel—the entry of the water into the tunnel ofa bow thruster of this vessel to be greatly reduced or avoided. Thepresence of a housing, of a recess and, naturally, of a bow thrustertunnel greatly disrupts the normal movement of boats and ships equippedtherewith, because this interruption in the hull of the vessel causeseddies, turbulence and a significant drag, reducing the speed ofmovement of the vessel and absorbing a large amount of the propulsionpower.

In order to avoid these disadvantages it has been proposed to closeoff—during normal movement of the vessel—the orifices in the hull whichgive access to the transverse tunnel in which the bow thruster/thrustersis/are housed, using sliding or pivoting shutters controlled by motors.These systems are not only expensive but are also very delicate becausetheir correct operation can be hampered by seaweed and rubbish of allkinds, and they thus require frequent and difficult maintenance.

The object of the present invention is to propose a device forcontrolling the flow of fluid passing in front of one or more orificesin the hull of a vessel, in particular at the orifices giving access tothe transverse tunnel enclosing the bow thruster/thrusters, in order toreduce the volume of fluid which flows along the hull of the vesselduring its normal movement entering or leaving this tunnel in order togreatly reduce or avoid any eddying, drag or turbulence phenomena, whichis simple, strong and requires only little or no maintenance. An objectof the present invention is the production of such a device forcontrolling the flow of fluid passing in front of an orifice or cavityin the hull of a vessel.

The object of the present invention is a device for controlling thefluid passing in front of the orifices in the hull of a vessel, inparticular those giving access to the transverse tunnel enclosing thebow thruster/thrusters, tending to obviate the disadvantages of theabove-mentioned existing devices and permitting the object stated aboveto be achieved. This device for controlling the flow of fluid passing infront of an orifice or cavity in the hull of a vessel is characterisedby the features listed in claim 1.

The attached drawing illustrates—schematically and by way of example—anembodiment of the device in accordance with the invention.

FIG. 1 is a schematic vertical partial cross-sectional viewperpendicular to the longitudinal axis of the vessel, passing throughthe axis of the bow thruster tunnel.

FIG. 2 is a partial view of the hull of the vessel in line with thearrow A of FIG. 1.

FIG. 3 is a cross-section along the line III-III of FIG. 2.

FIG. 4 is a cross-sectional detail on a larger scale showing the device.

FIG. 5 illustrates on a larger scale a transverse cross-sectional viewof the shapes forming a deflector.

The attached drawing shows very schematically the hull 1 of a vesselthrough which a bow tunnel 2 passes in the transverse direction, inwhich tunnel one or more bow thrusters 3 are mounted. At its ends thisbow tunnel 2 has orifices 4 passing through the hull 1 of the vessel andissuing entirely into the water. The cross-section of this bow tunnel 2is generally circular and its ends can be flared. The bow tunnel 2 isfilled with the fluid surrounding the hull 1 of the vessel. When thevessel manoeuvres in order to dock, for example, or in order to leaveits position at the quay, the bow thruster 3 is started up, which causesa displacement in the fluid inside the bow tunnel transverse to thelongitudinal axis of the vessel, which makes it possible to move thisvessel in order to bring it closer to, or move it further away from, themooring quay.

When the vessel is sailing normally the bow thruster is stopped and, ifno provision is made otherwise, turbulence is created in the proximityof the openings or orifices 4 of the bow tunnel, turbulence whichcreates a significant amount of drag. This drag reduces the speed of thevessel and causes excess consumption of fuel in propelling the vessel.

The object of the device in accordance with the invention is to controlthe flow of fluid passing in front of the orifices 4 of the bow tunnel 2in order to reduce or avoid entry of the fluid into this tunnel 2 andreduce or eliminate any turbulence and drag owing to the flow of thefluid in front of these orifices 4.

This device for controlling the flow of the fluid in front of theorifices of the bow tunnel 4 of the hull 1 of a vessel has at least onedeflector 5 rigidly fixed to the hull 1 of the vessel upstream of theorifice 4 and extending over a distance greater than or at least equalto the diameter of this orifice 4. This deflector 5 has, incross-section, a planar inner face 6 disposed facing the hull 1 of thevessel and a convex outer face 7. The thickness of the deflectorsincreases greatly in the upstream part 8 to then decrease slowly in thedirection of the downstream part and to terminate in a strongly taperedmanner forming a downstream edge 9.

This deflector 5 is rigidly fixed to the hull 1 of the vessel with theaid of supports 10 welded, bolted or fixed in any other manner to thehull 1 of the vessel.

The device preferably has two deflectors 5 disposed on either side ofthe orifice 4 of the bow tunnel 2. In this case the distance Lseparating the downstream edge 9 of the upstream deflector 5 from theupstream edge of the downstream deflector 5 a is substantially equal to,slightly less or greater than, the diameter of the orifice 4 of the bowtunnel 2.

The inner planar surface 6 of the deflectors 5 and 5 a is substantiallyparallel to the hull 1 of the vessel. In one variation the inner face 6of the upstream deflector 5 forms a slight angle with the surface of thehull 1 of the vessel so that its downstream edge 9 is further away fromthis hull than its front edge is. In this case the front edge of thedownstream deflector 5 a is closer to the hull 1 of the vessel than thedownstream edge 9 of this downstream deflector 5 a is.

Thus the passage produced between the upstream deflector 5 and the hullincreases in the direction of the orifice 4 and narrows for thedownstream deflector 5 a.

In the case where the device for controlling the flow of fluid has onlyone deflector, the downstream deflector 5 a is omitted.

If a bow orifice has a diameter of the order of 1 m, the length 1 of thedeflector/deflectors 5 would be of the order of 1.1 m, its depth P ofthe order of 15 to 40 cm and its thickness e of the order of 15 to 30mm.

When the device has two deflectors, one 5 upstream and the other 5 adownstream, the depth P of the upstream deflector is preferably greaterthan that of the downstream deflector.

When the vessel is moving forward in the direction of the arrow B, froma certain speed which is lower than the cruising speed of the vessel,the flow of fluid between the deflector/deflectors 5 and the hull 1 ofthe vessel is controlled and modified. It becomes uniform and controlledand forms a liquid wall in front of the orifice 4 of the bow tunnel,preventing the fluid from entering it or at least greatly reducing theentrance of fluid into the said orifice. This makes it possible toreduce or eliminate turbulence in the fluid at this location and toreduce the drag of the vessel very substantially.

The device of the invention is simple, inexpensive, fixed to the hull ofthe vessel and requires only a little maintenance while making itpossible to avoid drag and turbulence in the fluid owing to the presenceof the bow tunnel orifices and thus to reduce the resistance to theforward movement of the vessel.

The device described can be used to control the flow of fluid passing infront of any type of orifice or cavity formed in the hull of a vessel.

1. Device for controlling the flow of fluid passing in front of anorifice or cavity produced in the hull of a vessel, characterised inthat it has at least one deflector (5) rigidly fixed to the wall of thevessel upstream of the orifice or cavity; in that this deflector has aplanar inner face directed towards the hull of the vessel and a curvedouter face which is highly convex upstream and tapered downstream. 2.Device as claimed in claim 1, characterised in that it has a seconddeflector of a similar shape to the first, disposed downstream of theorifice or cavity.
 3. Device as claimed in claim 1, characterised inthat the planar inner face of the deflector is parallel to the hull ofthe vessel.
 4. Device as claimed in claim 1, characterised in that theplanar inner face of the deflector forms an angle with the hull of thevessel so as to create a space between this face and the hull whichnarrows or increases in the direction of the orifice or cavity. 5.Device as claimed in claim 2, characterised in that the distanceseparating the upstream and downstream deflectors is substantially equalto the diameter of the orifice or cavity.
 6. Device as claimed in claim2, characterised in that the planar inner face of the deflector isparallel to the hull of the vessel.
 7. Device as claimed in claim 2,characterised in that the planar inner face of the deflector forms anangle with the hull of the vessel so as to create a space between thisface and the hull which narrows or increases in the direction of theorifice or cavity.